Читать книгу Petroleum Refining Design and Applications Handbook - A. Kayode Coker - Страница 33

1 1. Line velocities (υ) and pressure drops (∆P): (a) For a liquid pump discharge, υ = (5 + D/3) ft/s and ∆P = 0.45 bar/100 m (2.0 psi/100 ft); (b) For liquid pump suction, υ = (1.3 + D/6) ft/s, ∆P = 0.09 bar/100 m (0.4 psi/100 ft); (c) for steam or gas flow: υ = 20D ft/s and ∆P = 0.113 bar/100m (0.5 psi/100 ft), D = diameter of pipe in inches.

2 2. Gas/steam line velocities = 61 m/s (200 ft/s) and pressure drop = 0.1 bar/100 m (0.5 psi/100 ft).

3 3. In preliminary estimates set line pressure drops for an equivalent length of 30.5 m (100 ft) of pipe between each of piece of equipment.

4 4. Control valves require at least 0.69 bar (10 psi) pressure drop for good control.

5 5. Globe valves are used for gases, control and wherever tight shut-off is required. Gate valves are for most other services.

6 6. Screwed fittings are used only on sizes 38 mm (1.5 in) or less, flanges or welding used otherwise.

7 7. Flanges and fittings are rated for 10, 20, 40, 103, 175 bar (150, 300, 600, 900, 1500, or 2500 psig).

8 8. Approximate schedule number required = 1000 P/S, where P is the internal pressure psig and S is the allowable working stress [about 690 bar (10,000 psi)] for A120 carbon steel at 260°C (500°F). Schedule (Sch.) 40 is most common.